docs: def run(self):
      """Builds a source distribution (sdist) package."""
      if self.formats != ["gztar"]:
        print("'setup.py sdist' unsupported format.")
        sys.exit(1)
  
      if glob.glob("*.tar.gz"):
        print("'setup.py sdist' remove existing *.tar.gz files from "
              "source directory.")
        sys.exit(1)
  
      command = "make dist"
      exit_code = subprocess.call(command, shell=True)
      if exit_code != 0:
        raise RuntimeError("Running: {0:s} failed.".format(command))
  
      if not os.path.exists("dist"):
        os.mkdir("dist")
  
      source_package_file = glob.glob("*.tar.gz")[0]
      source_package_prefix, _, source_package_suffix = (
          source_package_file.partition("-"))
      sdist_package_file = "{0:s}-python-{1:s}".format(
          source_package_prefix, source_package_suffix)
      sdist_package_file = os.path.join("dist", sdist_package_file)
      os.rename(source_package_file, sdist_package_file)
  
      # Create and add the PKG-INFO file to the source package.
      with gzip.open(sdist_package_file, 'rb') as input_file:
        with open(sdist_package_file[:-3], 'wb') as output_file:
          shutil.copyfileobj(input_file, output_file)
      os.remove(sdist_package_file)
  
      self.distribution.metadata.write_pkg_info(".")
      pkg_info_path = "{0:s}-{1:s}/PKG-INFO".format(
          source_package_prefix, source_package_suffix[:-7])
      with tarfile.open(sdist_package_file[:-3], "a:") as tar_file:
        tar_file.add("PKG-INFO", arcname=pkg_info_path)
      os.remove("PKG-INFO")
  
      with open(sdist_package_file[:-3], 'rb') as input_file:
        with gzip.open(sdist_package_file, 'wb') as output_file:
          shutil.copyfileobj(input_file, output_file)
      os.remove(sdist_package_file[:-3])
  
      # Inform distutils what files were created.
      dist_files = getattr(self.distribution, "dist_files", [])
      dist_files.append(("sdist", "", sdist_package_file))